TY  - JOUR
A1  - Riedl, Simon
A1  - Melnick, Daniel
A1  - Njue, Lucy
A1  - Sudo, Masafumi
A1  - Strecker, Manfred
T1  - Mid-Pleistocene to recent crustal extension in the inner graben of the Northern Kenya Rift
JF  - Geochemistry, geophysics, geosystems
N2  - Magmatic continental rifts often constitute nascent plate boundaries, yet long-term extension rates and transient rate changes associated with these early stages of continental breakup remain difficult to determine. Here, we derive a time-averaged minimum extension rate for the inner graben of the Northern Kenya Rift (NKR) of the East African Rift System for the last 0.5 m.y. We use the TanDEM-X science digital elevation model to evaluate fault-scarp geometries and determine fault throws across the volcano-tectonic axis of the inner graben of the NKR. Along rift-perpendicular profiles, amounts of cumulative extension are determined, and by integrating four new Ar-40/Ar-39 radiometric dates for the Silali volcano into the existing geochronology of the faulted volcanic units, time-averaged extension rates are calculated. This study reveals that in the inner graben of the NKR, the long-term extension rate based on mid-Pleistocene to recent brittle deformation has minimum values of 1.0-1.6 mm yr(-1), locally with values up to 2.0 mm yr(-1). A comparison with the decadal, geodetically determined extension rate reveals that at least 65% of the extension must be accommodated within a narrow, 20-km-wide zone of the inner rift. In light of virtually inactive border faults of the NKR, we show that extension is focused in the region of the active volcano-tectonic axis in the inner graben, thus highlighting the maturing of continental rifting in the NKR.
KW  - extensional tectonics
KW  - Kenya Rift
KW  - TanDEM-X DEM
KW  - DEM analysis
KW  - geochronology
KW  - normal faults
Y1  - 2022
U6  - https://doi.org/10.1029/2021GC010123
SN  - 1525-2027
VL  - 23
IS  - 3
PB  - American Geophysical Union
CY  - Washington
ER  -